The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Emulsifiable concentrate (EC) formulations are a favored liquid delivery system for agriculturally active compounds. Conventional EC's contain one or more active ingredients dissolved in a water immiscible solvent together with emulsifying surfactants. These solvents typically have very low solubility in water and have a high solubility for most agriculturally active compounds.
The presence of the solvent imparts significant advantages to the formulation, such as a higher degree of systemicity, which leads to higher overall biological activity as compared to other commonly used agricultural formulations such as wettable powders (WP), water dispersible granules (WDG) or suspension concentrates (SC). Such EC's are further easier to transport and store.
A good EC is not made using a simple formula that is transferable from active ingredient to active ingredient. It requires the formation of a stable emulsion upon dilution with water that does not separate upon standing.
Furthermore, there should not be any crystallization of the active compound from the EC after water dilution and the EC itself should be physically and chemically stable during extended storage periods, under wide conditions. It can further incorporate various adjuvants to increase the efficacy of the formulation, that must not disrupt the stability of the emulsion after water dilution.
Some major differential properties that lead to the better efficacy, stability and easier commercial use for EC's versus SC's may be described as; EC's are true solutions vs SC's which are suspensions, EC's are thermodynamically stable vs kinetically stable SC's, EC's have a much smaller particle size (<1 nm vs 2-5 um), the primary stabilization force for EC's is solution energy which is much greater than electrostatic and steric energy for SC's, and the lower intrinsic viscosity of EC's leads to Newtonian flow which is a key factor in non-clogging and even spread of herbicide during commercial sprayings.
Several publications describe the development of herbicidal emulsifiable concentrates, although Prodiamine itself has not been formulated into a commercial emulsifiable concentrate due to it's poor solubility in organic solvents and it's lack of ability to form a stable emulsion in water. More specifically towards the embodiments in the present invention, select publications have attempted to form or improve the emulsion properties of low solubility herbicides such as the dinitroaniline class of compounds, in which prodiamine can be loosely placed. For example, WO 98/48624 shows the improvement of the stability of the EC emulsion by the use of a high amount of a water-insoluble C6-C18 alkyl pyrrolidone. However, these C6-C18 alkyl pyrrolidone compounds are highly corrosive, have significant phytotoxicity and are too expensive for use in many agricultural applications.
U.S. Pat. No. 5,035,741 shows the use of fatty acids in the formulation of emulsifiable concentrates to improve the herbicidal activity of some compounds. U.S. Pat. No. 5,270,286 describes the formulation of a combination of imidazolinone and dinitroaniline herbicides as emulsifiable concentrates with the use of aromatic solvents and alkyl phenol polyethylene oxide condensates to improve solubility.
US20100279865 describes the formulation of a combination of many herbicides with Prodiamine in which ammonium sulfate is used to stabilize the colloidal solution and an oil soluble solvent is specifically excluded, due to the solubilization difficulties inherent in these molecules. US2011281731 describes the formation of an emulsifiable concentrate of dinitroaniline herbicides that avoids crystallization at low temperature and which comprises a diester co-solvent having the following formula R1OOC—(CH2)n—COOR2.
US2005113253 and JP7109193 describe fertilizer compositions that contain Prodiamine but specifically do not describe the potential use of an EC formulation to achieve a superior composition and distributed product. These and other publications in the prior art, describe the inherent difficulty in producing a commercially viable EC formulation and may be instructive for the absence of a commercial EC formulation containing Prodiamine herbicide as the primary active ingredient. Further, none of the above publications provides for a method to produce a stable, low phytotoxic, environmentally friendly emulsifiable concentrate formulation of Prodiamine, which can be used, directly or indirectly, for superior weed control.